Yesterday the European Court of Human Rights (ECtHR) halted Boris Johnson's plan to deport asylum-seekers to Rwanda with a dramatic last-minute ruling.
The intervention drew both praise and condemnation across the UK, with the government vowing that another flight would take place.
But what is the ECtHR? And why was it set up?
What is the ECtHR?
The ECtHR is an international court based in Strasbourg, France.
It was established to enforce the European Convention on Human Rights (ECHR), an international treaty designed to protect human rights and basic freedoms in Europe.
Forty-seven states signed up to the ECHR, including the bulk of Europe, alongside Russia and Turkey.
Any person who feels that their rights enshrined in the ECHR have been violated by a state can take their case to the court.
If judges at the ECtHR find that someone's rights have been violated, it can rule against a state and order them to pay compensation.
The member state may also have to take steps to ensure the same thing does not happen again.
However, the court is not empowered to overrule national decisions or annul national laws.
When was it founded?
The ECHR and court were established by the Council of Europe, an international organisation founded after World War II (WW2) to protect human rights, democracy and the rule of law in Europe.
Both have nothing to do with the European Union (EU), as has mistakenly been claimed by opponents of Tuesday's ruling against the Rwanda deportation.
They are fully independent from states and international institutions.
British lawyers, notably MP Sir David Maxwell-Fyfe, played a leading role in drafting and implementing the ECHR, which was signed in 1950.
The contribution of Maxwell-Fyfe, who had been a prosecutor at the Nuremberg trials of Nazi war criminals, was such that he has been described as "the doctor who brought the child to birth."
Britain's wartime leader Winston Churchill was a staunch advocate of the ECHR, believing it played a key role in protecting citizens from cruel and inhumane treatment by despotic governments within continental Europe.
The UK was the first signatory to the ECHR.
What does the ECHR protect?
The ECHR protects the rights of every citizen within a signatory state.
These rights are divided into 19 separate articles.
Article 5, for example, guarantees everyone the right to liberty and security. Whereas Article 6 ensures people have a right to a fair trial and Article 8 protects individual's privacy.
The ECtHR blocked the UK's deportation flight to Rwanda under Article 3 of the ECHR which prohibits torture without exceptions or limitations.
It found that there was a real risk of inhuman and degrading treatment if the asylum-seekers, most of whom are from the Middle East, were sent to the east African country.
Police violence and poor conditions in detention can often constitute torture under Article 3.
During a debate over whether these rights in the ECHR should be legally enforceable, Maxwell-Fyfe said: "We cannot let the matter rest at a declaration of moral principles and pious aspirations, excellent though the latter may be.
"There must be a binding convention, and we have given you a practical and workable method of bringing this about," he added.
Have any states ever left the ECHR?
Only two countries have ever withdrawn from the ECHR.
In 1969, Greece withdrew from the Council of Europe, following a military coup which abolished democracy and imposed a junta, bringing the country into conflict with the organisation.
It later rejoined in 1974, when the "rule of the colonels" ended in Greece.
Russia is the second country. It was expelled by the Council of Europe on 16 March 2022 over its invasion of Ukraine.
Arguments that the UK should leave the ECHR have circulated in the country for years.
In 2016, former Prime Minister Theresa May said the UK should withdraw from the ECHR, arguing that it "bind[s] the hands of parliament, adds nothing to our prosperity, makes us less secure by preventing the deportation of dangerous foreign nationals.
"[It] does nothing to change the attitudes of governments like Russia’s when it comes to human rights,” she added.
Defenders of the ECHR and the court have said they ensure the atrocities of WW2 are never repeated, protect the most vulnerable, help challenge injustices and act as a system of checks and balances against governments.